A parameter known as the Siple Windchill Index has become relatively popular in determining cold stress experienced by persons in cold, windy air environments. This is especially so in winter. Convective heat loss, for example, as experienced by persons in a cold air environment is not just a function of the air temperature. The wind speed in that environment is also an important consideration.
The windchill index as determined from measurements of wind and dry bulb air temperature provides either (a) the still air temperature equivalent in cold stress, to that produced by the measured temperature and wind combination; or (b) the convective heat loss from exposed human flesh caused by the particular combination of wind and air temperature. Both of these indices are useful. They can be used to gauge an anticipated time of exposure before dire physiological events occur, such as frostbite of exposed flesh.
At present, for example, the windchill index is usually determined by taking at least three separate actions. Two are measurements of meteorological phenomena, namely, wind speed and air temperature. These two measurements are made with different instruments. With these measurements, a chart or nomogram must be consulted to determine the windchill value.
These multiple actions are unnecessarily long and complicated processes. Further, they can be subject to error. This danger or risk arises because the measurements of conditions must be manipulated mentally through a number of steps, to arrive at a windchill value. The calculation occurring at each step carries a possibility for error with it.
The present invention is expected to overcome many of the shortcomings mentioned above. This invention provides a device which is simple to use. Further, it minimizes the separate steps which need to be taken and thus reduces the risk of introducing errors. Thus a user of this invention can simply and reliably obtain measurements of equivalent windchill temperature and heat loss.
Accordingly, there is provided by this invention a portable measuring device to provide a readout representing an equivalent windchill temperature or heat loss in cold moving air; said device comprising; a body having walls therein to define a channel through which moving air is conducted, an oppositely disposed pair of such walls being at least partially transparent; a windvane disposed in said channel for deflection by said air moving therethrough, said windvane being pivotally supported from said body; a thermometer also supported from said body, and having graduations thereon to provide a measurement of temperature of said air; and chart means supported by said body, visible through one of said transparent walls, said chart means including first, second, and third series of markings thereon, at least a portion of one of said series of markings being in alignment with the graduations on said thermometer, and at least a portion of an other of said markings being oriented to be in alignment with the windvane upon deflection thereof, the one and other series of markings being arranged to provide an intersection thereof readable against the remaining series of markings, thereby to yield from said remaining series of markings said readout, selectively, of the windchill temperature and heat loss.
These and other features and advantages of this invention will become apparent from the detailed description below.